Hey! Not only am I an artist, but ye olde day job is as a systems engineer, so this is right up my alley.
Dropbox is actually a really good place to go (I was going to suggest it when I read the title lol). They do a lot of regular backups, and even offer the ability to restore old files. I can't tell you how many times I've accidentally deleted my file in dropbox and been able to go back to previous versions and get it back. It's a really good option, and unless you're working on something for hours without saving it (don't do that, anyway! lol) I don't think you'd stand to lose much if DB went down, and it would take a lot for the storage side of it to go down (not the network side, but the storage side for sure). They've got redundant file systems and massive storage servers configured to prevent just such an occurrence. I've never lost any files working with DB. So I think you've already got a pretty good solution in place
-Aaron